This page presents some ideas for expressing NDVI in terms of population density for the City of Denver, Colorado.

1 Population density

A map of population density by block group per 2016-2020 American Community Survey 5-year Estimates

Population density tertiles

2 NDVI

A map of NDVI of each block group. Note NDVI is measured using Landsat-8 at a spatial resolution of 30 meters squared on July 4, 2021, a cloud-free day. The weighted average NDVI of each block group excludes bodies of water.

NDVI tertiles, overall

3 Explore relationship between population density, NDVI, and equity indices

3.1 Scatterplot of population density x NDVI

3.2 Scatterplot of equity index (CDPHE definition) x NDVI x pop. density tertile

3.3 Scatterplot of equity index (Denver definition) x NDVI

3.4 Scatterplot of equity index (CDPHE definition) x pop. density

4 Possible composite measures considering both population density and NDVI

  1. Population density per NDVI (population density per square mile / NDVI)
  2. A ranking of population density per NDVI
  3. Tertiles of NDVI within tertiles of population density

4.1 Population density per NDVI

The first is difficult to visualize on a map because the distribution has a right skew with some very high values and most much lower.

##     Min.  1st Qu.   Median     Mean  3rd Qu.     Max.     NA's 
##    457.5  14482.2  22057.3  35548.7  36465.0 364573.0        8

4.2 Ranking of population density per NDVI

The second is easier to visualize because the distribution is uniform by definition (a simple rank).

##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max.    NA's 
##     1.0   131.5   262.0   262.0   392.5   523.0       8

Map population density per NDVI and the ranking of population density per NDVI on the same map.

4.3 NDVI tertiles within pop. density tertiles

4.3.1 Map of NDVI tertiles within tertiles of population density

4.3.2 Maps of ratios and differences of relative NDVI within tertiles of population density (highest NDVI tertile is referent)

Ratio of block group NDVI compared with the median NDVI of the highest NDVI tertile in that population density tertile

Difference of block group NDVI compared with the median NDVI of the highest NDVI tertile in that population density tertile



Copyright © 2022 Michael D. Garber